Today's locomotive is fast becoming a complex communications system incorporating voice, distributed power control, DGPS, digital data links and sensor data communications. The complexity of this environment will continue to increase with the advent of new positive train control systems, and other equipment designed to improve safety and efficiency of the locomotive. Many of these systems have been added to the train over a period of years as different technologies were developed and matured and other new technologies became available. One component common to all of these systems is the antenna. It may be a different size and shape depending on the frequency of operation, but the installation site is always the same.
Typically locomotives in the railroad transportation industry need to be equipped with radio communication systems of different types, GPS, Cellular, PCS, and RF at different communication frequencies (bands). Each communication system needs its own antenna resonant at the desired frequency(s) which is mounted to the roof of the locomotive cab, and then cabling from the antenna feeds through an access hole drilled into the roof to its respective communication system or apparatus. Each antenna needs to be at a suitable location so as not to interfere with each other antenna or cabling of other communication systems. Mounting multiple antennas for different radio system is time-consuming and requires many man hours. For example, mounting just 5 antennas requires at least 5 holes in the roof of the cab for mounting hardware. Further problems often arise when there are multiple antennas to be installed and all of them are targeting the same installation site of the top (or roof) of a locomotive. This is due to the fact that the available ground plane (the top or roof of the locomotive cab) is limited in space, and there are other mechanical systems, such as hand holds, signaling devices, etc. . . . , that need to be there.
Further, there is a need not only to install multiple different antenna systems operating different frequencies or band on new locomotives, but to retrofit existing locomotives that will require these new antenna systems despite the limited space, which can results in a major, very costly overhaul.
It would be desirable to provide an antenna array having multiple antenna elements that is optimized at desired resonant frequencies or bands for locomotive communication systems which can be installed at the same time so as to reduce the cost, time, and labor of installation, and minimizes the number of access holes or opening drilled in the roof of the locomotive. Further is would be desirable to provide such antenna array which can be used both singularly, and in pairs, on the same locomotive, while allowing existing rooftop structures and existing antenna(s), or other system(s) to remain intact.